Ostrość wzroku jest ważna.

Because Polish often expresses meanings like the sharpness of vision, the quality of hearing, the color of the sky with a noun followed by another noun in the genitive case.

So:

• wzrok = eyesight, vision
• wzroku = of eyesight / of vision

That means:

• ostrość wzroku = sharpness of vision / visual acuity

This is a very common Polish structure.

Ostrość is in the nominative singular, because it is the subject of the sentence.

The basic structure is:

• Ostrość wzroku = the subject
• jest = is
• ważna = important

So literally: Visual acuity is important.

Because ważna must agree with ostrość, which is a feminine singular noun.

Polish adjectives change to match the noun in gender, number, and usually case.

Here:

• ostrość = feminine singular
• so the adjective must be ważna = feminine singular

Compare:

• ważny = masculine singular
• ważna = feminine singular
• ważne = neuter singular

A good clue is the ending and the dictionary form. Ostrość is one of many Polish feminine nouns ending in -ość.

Examples:

• ważność = validity
• jakość = quality
• długość = length
• ostrość = sharpness

These are typically feminine.

Jest means is. It is the 3rd person singular form of być (to be).

So:

• jest = is

In this sentence it links the subject and the description:

• Ostrość wzroku = visual acuity
• jest ważna = is important

Sometimes Polish does omit forms of to be, especially in informal style, headlines, notes, or certain fixed expressions. But in a normal full sentence like this, jest is the standard and most natural choice:

• Ostrość wzroku jest ważna.

You might occasionally see Ostrość wzroku ważna in a very compressed style, but that is not the neutral everyday version learners should copy first.

Not completely. Polish word order is more flexible than English, because case endings help show grammatical relationships.

The neutral order here is:

• Ostrość wzroku jest ważna.

But other orders are possible for emphasis, for example:

• Ważna jest ostrość wzroku. = What is important is visual acuity.

So the original sentence is the most straightforward, neutral version.

A rough pronunciation guide is:

• ostrość ≈ OS-troshch
• wzroku ≈ VZRO-koo
• jest ≈ yest
• ważna ≈ VAZH-na

A few useful sound notes:

• ś / si is a soft sh-like sound
• rz usually sounds like zh as in measure
• w in Polish sounds like English v
• j sounds like English y

So the whole sentence sounds roughly like:

OS-troshch VZRO-koo yest VAZH-na

Polish allows consonant clusters that feel unusual to English speakers. In wzroku, the beginning wzr- is normal in Polish.

Remember that Polish w sounds like v, so wzroku begins roughly vzro-, not wzro- in the English sense.

It may help to practice it in parts:

• wzro-
• -ku

Then say it smoothly: wzroku.

Yes. It is a normal and common expression in medical, optical, and everyday contexts.

You may see it in phrases like:

• badanie ostrości wzroku = vision acuity test
• pogorszenie ostrości wzroku = deterioration of visual acuity
• poprawa ostrości wzroku = improvement of visual acuity

So this is a very useful phrase to know.

Yes, but it means something slightly different.

• Ostrość wzroku jest ważna. = Visual acuity / sharpness of vision is important.
• Wzrok jest ważny. = Sight / eyesight is important.

The first focuses on the quality or sharpness of vision. The second refers more broadly to vision or the sense of sight.

It follows a very common Polish pattern:

noun phrase + jest + adjective

Here that gives:

• Ostrość wzroku = noun phrase
• jest = is
• ważna = adjective

So once you know this pattern, you can build similar sentences:

• Muzyka jest ważna. = Music is important.
• Zdrowie jest ważne. = Health is important.
• Dobra pamięć jest przydatna. = A good memory is useful.